The preventive effect of green tea on the gap junction intercellular communication in renal epithelial cells treated with a renal carcinogen

Objective: Clinical studies imply that (-)-epigallocatechin-3-gallate (EGCG), a main ingredient of green tea catechins, has a chemopreventive action against cancers and suppresses the proliferation of cancer cells. However there is no report about its chemopreventive effect for renal cancer. We previously determined that renal carcinogens suppressed the gap junction intercellular communication (GJIC) of renal epithelial cells. In this study, we investigated the effect of EGCG on the GJIC of renal epithelial cells treated with a renal carcinogen. Materials and Methods: Mardin-Darby canine kidney (MDCK) cells were used to determine the protective effects of EGCG on dimethylnitrosamine-induced alteration of GJIC and connexin 43 (Cx 43). The maximum concentration of EGCG was determined by the lactate dehydrogenase assay method. The scrape-loading dye transfer method was used to assess the expression and cellular localization of Cx 43. The phosphotylation status of Cx 43 was determined by Western blot analysis. Results: The optitnal noncytotoxic concentration of EGCG was determined to be 10 mug/ml. The levels of GJIC and Cx 43 expression were markedly decreased in MDCK cells exposed to dimethylnitrosamine. A 12-h pretreatment with EGCG greatly ameliorated the GJIC-inhibitoty effects of diniethylnitrosainine. Conclusion: These results suggest that the preservation of GJIC may indicate the chemopreventive effect of green tea on renal epithelial cells treated with a renal carcinogen in vitro.